Whatever the connection, infants are spending an increased amount of time in front of the TV, according to a team led by Dr. Dimitri A. Christakis of the Center for Child Health, Behavior and Development at the University of Washington.

A 2003 report from the Henry J. Kaiser Family Foundation found that each day, 68 percent of American infants viewed some type of electronic medium: TV programming, DVDs or video tapes, computers or video games.

To determine the impact of infant TV watching, the Christakis group recruited parents who agreed to equip their 2- to 24-month-old kids with a wire for one day a month in order to record every sound for a 12- to 16-hour period.

Using noise-detection software that analyzed at least one recorded session from each of the 329 youngsters, files were sorted into sounds the kids heard and sounds the kids made.

The researchers used a statistical model to determine the association between audible television and the number of words spoken by each adult and each child. They also examined how many meaningful vocal interactions were shared by the child and adult while the TV was on.

They found that each hour spent with a TV was associated a significant reduction in a child's own attempts to talk.

Likewise, for each hour in front of the tube, the child heard 770 fewer words from an adult. That's 7 percent fewer than the average number of words a child hears in a household when the television is off.

TV May Present Toddlers With Distractions

"Some of these reductions are likely due to children being left in front of the television screen, but others likely reflect situations in which adults, though present, are distracted by the screen and not interacting with their infant in a discernible manner," the researchers concluded.

The authors said 30 percent of households have a TV on at all times, which brings up the question, How many opportunities for child-parent communication are being missed?

Previous research has shown that when adults are watching their own programs -- even a show like Jeopardy, which would be mere background noise to an infant -- the grownups communicate less with their children, and the kids make less noise themselves, said Deborah Linebarger, a researcher at the University of Pennsylvania who has studied the effects of media on young children.

Linebarger was not affiliated with the study.

The authors of the latest report acknowledged that their findings seem obvious: More TV time equals less human interaction. But they say it might also debunk the claims of companies that market DVDs for infants suggesting that their products promote child-parent interaction.